What Do These Mean?

I'm trying to construct an entry for the Wicked Lasers contest, however I keep on finding the same letters on several diagrams... 

Can anyone tell me what the G, S and D stand for?

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thomas9666 (author)  steveastrouk6 years ago
Thanks.... But what do these mean?

Sorry for being stupid, electronics isn't taught for another 2 years at my school.
If you're building from an existing diagram, just follow it. Like Sean says, its a MOSFET, a field effect transistor, how it works is tricky to understand.
The device is a Field Effect Transistor, a type of transistor that uses an electric field to change the impedance from drain to source from near-infinite to near zero. They can be used as switches and amplifiers, amongst other uses.

A voltage is applied to the Gate terminal to determine the state of the drain/source impedance.

IMO, you should google it or go to wikipedia for a lengthy answer.

thomas9666 (author)  steveastrouk6 years ago
And can you explain this very simply....
76543216 years ago
A current at the gate makes current flow from the drain to the source (yes the names sound backwards)
NO There is no steady gate "current" MosFETs are voltage driven at the control, unlike BJTs.


In fact, for all intents and purposes, (and aside from hair-splitting) there isn't any current at the gate, steady or otherwise.

FETs are voltage controlled devices.

A BJT however, can be (in some ways) modeled after a venturi. Flow (literal) from the Base to emitter is necessary to switch the collector/emitter flow. And in fact it is directly proportional to that flow by the Hfe
Me ? Split hairs ?
I WAS thinking of gate capacitance charging.

oops. NO I didn't mean you were splitting hairs. was just trying to imply that yeah...there may be current, but it's tiny and simply a parasitic rather than a causal like in a BJT.

Just trying to keep my comment in the thread rather than making it possibly non-sequitur by posting separately...
Its alright, I am a champion hair-splitter ;-)

HA! I was right then. you woulda caught me on it if I hadn't added that qualification. NYAH! ;-)

(as if I'm anyone to talk)
He he he
The gate voltage (not current) does not make anything happen other than to reduce the impedance of the semiconductor junction.
7654321 76543216 years ago
Actually I think it can go both ways, nevermind